VM debugger: fix closures in mixed-in functions

tests/standalone/debugger/mixin_closure_debugger_test.dart

Index: tests/standalone/debugger/mixin_closure_debugger_test.dart
===================================================================
--- tests/standalone/debugger/mixin_closure_debugger_test.dart	(revision 0)
+++ tests/standalone/debugger/mixin_closure_debugger_test.dart	(working copy)
@@ -0,0 +1,54 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// This test forks a second vm process that runs this dart script as
+// a debug target.
+// Run this test with option --wire to see the json messages sent
+// between the processes.
+// Run this test with option --verbose to see the stdout and stderr output
+// of the debug target process.
+
+// This test checks that a breakpoint can be set and is hit in a closure
+// inside a mixin function. Regression test for issue 15325.
+
+import "debug_lib.dart";
+
+class S { }
+
+class M {
+  m()  {
+    var sum = 0;
+    [1,2,3].forEach((e) {
+      sum += e;  // Breakpoint here.
+    });
+    return sum;
+  }
+}
+
+class A = S with M;
+
+main(List<String> arguments) {
+  if (RunScript(testScript, arguments)) return;
+  var a = new A();
+  print(a.m());
+}
+
+// Expected debugger events and commands.
+var testScript = [
+  MatchFrame(0, "main"),  // Top frame in trace is function "main".
+  SetBreakpoint(23),      // Set breakpoint inside the forEach closure.
+  Resume(),
+  MatchFrames(["S&M.<anonymous closure>", "forEach", "S&M.m"],
+              exactMatch: false),  // First iteration.
+  MatchLocals({"e": "1"}),
+  Resume(),
+  MatchFrames(["S&M.<anonymous closure>", "forEach", "S&M.m"],
+              exactMatch: false),  // Second iteration.
+  MatchLocals({"e": "2"}),
+  Resume(),
+  MatchFrames(["S&M.<anonymous closure>", "forEach", "S&M.m"],
+              exactMatch: false),  // Third iteration.
+  MatchLocals({"e": "3"}),
+  Resume(),
+];